<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Vue data update</title>
    <script src="../../vue.js"></script>
</head>
<body>
   <div id="app">
       <div v-if="isShow" ref="self">test</div>
       <button @click="isShow=!isShow">update</button>

   </div> 
   
   <script>
       var vm=new Vue({
           el:'#app',
           data:{
               isShow:false
           },
           beforeUpdate(){
               console.log("before update!")
               console.log(this.$refs.self)
           },
           updated(){
               console.log("after updated!")
               console.log(this.$refs.self)
           }

       })

   </script>
</body>
</html>